By Alistair Grant

IT was the so-called “youthquake” – a phenomenon so powerful it was chosen as Oxford Dictionaries’ word of the year.

When Theresa May was unexpectedly deprived of her majority in 2017, fingers pointed to a surge in young people registering to vote and backing Labour.

Just days after the general election, the fields of Glastonbury’s world-famous festival erupted to chants of “Oh, Jeremy Corbyn!”

But research later suggested young people did not sway the last election. In fact, the British Election Study found there was little change in turnout by age group – although this conclusion has been questioned by others.

A rise in people registering to vote over the last few weeks, particularly among the under-34s, has again raised questions over the impact of the young on the UK’s political future.

Tomorrow, a Question Time special – which will be broadcast at 8.30pm across BBC One, BBC Radio 1 and 1Xtra – will allow a selected audience of under-30s to quiz party figures.

Professor Sir John Curtice, the UK’s foremost polling guru, said an “iron rule of politics is that young people are less likely to turn out and vote”.

He added: “But I would say there’s potential room for the gap to narrow, even if it doesn’t disappear entirely.”

He said younger voters are still more likely to vote Labour, although the picture is different in Scotland due to the success of the SNP.

“Across the UK as a whole, the more young people turn out to vote the better the prospects are for Labour,” he said.

Mark Diffley, an independent pollster and former Ipsos Mori Scotland director, said UK-wide polling shows “a very linear relationship between your age and who you are likely to support”.

He said: “The younger you are, the more likely you are to support Labour, and the older you are, the more likely you are to support the Tories.

“That is absolutely baked in to the data. It doesn’t really matter which poll you look at ... that is a feature of all the polling that we see to various degrees. Age is definitely a key factor.

“And it’s also true to say, therefore, that the higher the turnout among young people, then absolutely the better Labour would expect to do.”

Mr Diffley pointed to a recent YouGov poll, which showed about 50 per cent of 18-24-year-olds said they would vote Labour on Thursday, with only 20% backing the Conservatives.

Among the oldest age group – those over the age of 65 – it found 66% said they would vote Tory. Just 13% said they would plump for Jeremy Corbyn’s party.

Mr Diffley is wary of stereotypes when it comes to the reasons behind low youth turnout.

Habit plays a part, he said. If you have voted before, you are more likely to do so again.

He added: “For some it will be a lack of interest, for others it might be that they live more mobile lifestyles and so forth, either [through] studying or travelling they are less rooted in one place.

“There’s probably a variety of reasons. It was less so in the independence referendum, where there was an age effect but it was much less marked than it was in regular elections.

“So maybe there’s something in there as well – if they think there’s something actually worth voting for, particularly on a national, binary question, then perhaps they will be more motivated to take the time to register and then to actually turn out.”

He continued: “Interestingly, the turnout in the last two general elections has been marginally higher in Scotland than it has been in other parts of the UK, which to me suggests that this theory of once you’ve voted you get into the habit of it probably does have some credence to it.

“People who made the effort to register in 2014, who wouldn’t have done otherwise, a lot of them will have continued to use their vote in 2015 and then again in 2017, and may do again this year as well – although those effects clearly wear off, to come extent, over time.”

But just because they might not swing the national result, that doesn’t mean young people can’t have an impact.

In constituencies such as Canterbury, where Labour has a majority of 187, the high density of young voters could have a big impact.

Mr Diffley points to two key seats in Scotland where the student vote could prove crucial – Stirling and North East Fife.

The latter is home to St Andrews, a town dominated by its ancient university. It is also the UK’s most marginal constituency.

The SNP’s Stephen Gethins is defending a majority of just two, with the Scottish Liberal Democrats determined to overturn this. Both parties are avowedly pro-Remain.

Stirling also has a healthy student population. The Tories’ Stephen Kerr has a majority of 148 there, and the SNP’s Alyn Smith will be hoping to hoover up the anti-Brexit vote. A chunk of this will be found in the university.

NUS Scotland has engaged in voter registration drives across the country, attending campuses to sign students up to the electoral register.

President Liam McCabe said: “An incredible 2.6 million 18 to 35-year-olds have signed up to vote since the general election was called.

“Ahead of election day, NUS Scotland will be out across the country encouraging all students to make a plan on how they’re going to vote to ensure they set aside time to do so.

“For this generation, there has never been a higher-stakes election. Whether it's the climate emergency, Brexit or the cost of living, everything is on the table and every vote counts.”

Robyn Graham, 18, is the national organiser for Young Scots for Independence and an SNP member since 2017. For her and many others of her generation, climate change looms large.

She said: “That’s something that’s really very important to me in this General Election – the fact that [the SNP] have taken the facts and recognised the activism of young people and decided to translate that into their manifesto commitments.

“I think it’s the most important issue for young people – protecting the planet they live in.”

Ms Graham said more young people are taking politics seriously, because they have realised “how tangible politics is in their everyday lives, how much it does actually have a stake in their lives”.

She said many have friends and partners who are EU nationals, and benefit from schemes such as the Erasmus programme to help students study abroad.

“It’s things like this that are going to have a very real, visible effect on people’s lives, which makes them want to get out and vote, and which is causing them to become engaged,” she added.

But young or old, Mr Diffley said the sheer number of marginal seats in Scotland should motivate people to get out and vote on polling day.

“What should encourage people to vote in Scotland are the number of marginal seats,” he said.

“A quarter of the seats in Scotland have majorities of less than 1,000, so actually that really should be a motivator – not just for young people, but for everyone.

“Because if you live in North East Fife, your vote really does count, as it does in lots of other places which aren’t quite as marginal as that, but which are nonetheless very marginal.

“So for those who look at these things, which of course may not be everyone, there is a sense in quite a few places in Scotland that a single vote could be seen as being quite powerful this time.”